As an apparatus (method) of changing a display direction on a screen of an electronic device, a technique of changing a display direction on a screen when an angle indicated by an angle meter satisfies a predetermined condition has been widely used. For example, a technique described in Patent Document 1 provides a portable electronic device that can instantaneously change a screen direction according to an intention of a user.
A photosensor-equipped unit including a light environment measuring sensor that measures illumination, correlated color temperature, and color rendering properties by receiving light including light from an illumination device or sunlight, or a color measuring sensor that measures a color of a sample to be measured by illuminating the sample and receiving light from the sample at a predetermined angle has widely been used as a photometric apparatus having a display function by being connected to a portable electronic device (display processing terminal device) via a general-purpose interface.